1. Field of the Invention
The invention disclosed relates to electric vehicle supply equipment.
2. Discussion of the Related Art
Plug-in electric vehicles (EVs), including all-electric cars, neighborhood electric vehicles and plug-in hybrids, are becoming a popular mode for personal transportation, in part because they are less expensive to operate and have a reduced carbon footprint. Electric vehicle charging stations, also called Electric Vehicle Supply Equipment (EVSE), provide power to an EV through a standardized interface. The interface is defined by industry standard SAE J1772. The interface includes defined control signals, ground, and a high ampere current path. In the Level 2 alternating current (AC) charging standard, the EVSE may provide up to 80 A charging current to the connected EV.
The high ampere current path includes multiple junctions between conductors. The connection point between the cordset handle or charging handle of the EVSE and the receptacle of the EV is an example of a pin and socket junction. The construction of the EVSE charging handle commonly includes junctions that connect the wires of the cordset cable and the pins of the handle.
These multiple junctions represent opportunities for resistive heating along the current path between the EVSE and EV. For example, with manufacturing tolerances, mechanical ageing and reduction of contact pressure, chemical corrosion or oxidation of mating surfaces, or misuse and abuse leading to degraded performance, the current path within the EVSE charging handle can become increasingly resistive. Increased resistance may lead to overheating and possibly melting the charging handle while the handle is fastened to the EV during charging operations.
The present version of the J1772 does not require any monitoring of the temperature in the current path. However, with the possibility of degraded performance at the junctions in the EVSE cordset caused by heating, it would be advantageous to monitor the temperature of the charging handle. Knowing the temperature of the charging handle would allow for remediation, such as reducing the charging rate, aborting the charging session, or alerting the owner/operator for maintenance to be performed.
Present solutions for monitoring the temperature within the EVSE charging handle require additional, dedicated connection components between a temperature measurement device and the EVSE electronics. These include using additional conductors within the EVSE cord beyond those specified by the J1772 standard, or alternately using a wireless data transmission from the measurement device in the handle to the electronics of the EVSE. Present solutions to achieve temperature monitoring are prohibitively expensive and complicated to implement in the EVSE.